Ground stabilisation is a descriptive term for the enhancement of soil which, by virtue of its nature or changes to its properties, has become unstable or insufficiently strong to carry required loads or be stable. Factors which affect the stability of soil include loss of lateral support, removal of fine grains by washout from flowing water, decay of organic materials in the soil, changes in soil moisture content and progressive soil compaction over time, and/or movement of soil under pressure or down a gradient.
Conventional piles require end bearing capability or friction or both, to provide support. To achieve this, a pile must either be of a sufficiently large diameter, to provide sufficient end bearing capabilities or have a mechanically profiled surface in order to enhance its friction against the soil. In some circumstances both features are employed in a pile so as to impart the desired load bearing characteristics.
In order to drive piles with the desired load bearing capabilities, in situ, powerful and often large equipment is required to install the piles. This large equipment or heavy plant can sometimes pose serious problems in some situations, for example where access is limited or costs are prohibitive.
Also use of larger diameter piles results in the pile needing to be located farther from a centre line of a structure, such as a foundation or wall, which in turn requires that the piles themselves need to be stronger for the same application. A consequence is that the location of such large piles is not always at the desired or optimum position.
Permeation grouting is a process of improving ground stabilisation by filling interstitial gaps between particles of soil with a liquid, such as grout, cement, polyurethane or other resinous substance, that subsequently sets or cures, as a solid. The process requires that the soil be sufficiently porous to receive the resinous substance or liquid. Soils, such as fine silt and clay are termed cohesive and cannot normally be permeation grouted. However, silt and clay formations are commonly found beneath foundations of buildings, either in layers or as discrete pockets.
Such layers or pockets tend to disrupt or ‘break’ the continuity of a permeation grouted column, rendering all permeation grouted soil below the so-called ‘break’ redundant and therefore only capable of providing limited improvement in ground stability.
The present invention arose in order to overcome problems associated with existing ground stabilisation systems and to provide an improved ground stabilisation system.